Question

Lets say I have a Timer which has the Elapsed event handled. What thread is the method code executed on?

Is is the thread that the timer was created on? If so, that means if I wish it to be on another thread I have to ensure that the timer gets created in the threads main loop rather than the initialization of the thread – correct?

Answer 1

The thread is one out of the threadpool. There is no way to prodict which thread will be associated with the elapsed method.

Details: http://msdn.microsoft.com/en-us/library/system.timers.timer.elapsed.aspx

(And it should not matter, from a designs perspective)

Edit: Actually there is a method to define which thread is used; You can used the SynchronizingObject property of the timer:

When SynchronizingObject is null, the method that handles the Elapsed event is called on a thread from the system-thread pool. For more information on system-thread pools, see ThreadPool.

When the Elapsed event is handled by a visual Windows Forms component,
such as a button, accessing the component through the system-thread
pool might result in an exception or just might not work. Avoid this
effect by setting SynchronizingObject to a Windows Forms component,
which causes the method that handles the Elapsed event to be called on
the same thread that the component was created on.

See: http://msdn.microsoft.com/en-us/library/system.timers.timer.synchronizingobject.aspx